Method and apparatus for mechanically balancing the disk pack of a hard disk drive

ABSTRACT

The invention includes a method making a balanced disk pack for a hard disk drive, from a disk pack including a spindle motor rigidly coupled, and aligned by at least two open screw holes, with a disk clamp. The invention includes the resulting balanced disk packs, as well as hard disk drives built with such balanced disk packs. The invention also includes apparatus providing the means for implementing the steps of making a balanced disk pack from a disk pack. The invention includes at least one mechanical counterbalance for use in balancing the disk pack of a hard disk drive.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of patent application Ser.No. 10/657,587 filed Sep. 8, 2003 now U.S. Pat. No. 7,064,923 whichfurther claims the benefit of the priority date of U.S. provisionalpatent application Ser. No. 60/413,734, filed Sep. 25, 2002, thespecification of which is hereby incorporated in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to mechanically balancing the disk pack ina hard disk drive.

2. Background Information

Hard disk drives contain a plurality of magnetic heads coupled torotating disks. The disk pack rotates the disk surfaces in a hard diskdrive. Imbalances in the disk pack adversely affect communication to andfrom the rotating disk surfaces. Therefore, disk packs must be balancedto minimize rotational variation at the disk surfaces.

The typical prior art disk pack includes a spindle motor, one or moredisks, possibly one or more spacers, and a disk clamp. Bolts or screwscouple the disk clamp to the spindle motor, acting to clamp the disk(s)and spacers into a rigidly coupled assembly which is rotated by thespindle motor during operation.

Making disk packs includes a rotational balancing process, whichmechanically aligns the disk packs by attaching counterbalances. Atypical balance tolerance for a disk pack is a variation in angularmomentum of 35 milligram-centimeters, as measured by a balancecalibration system.

There are several existing approaches to balancing disk packs based upondifferent counterbalances. These existing approaches have createdproblems, which have added to the cost of production and/or diminishedthe reliability of the produced hard disk drives.

A first prior art balancing approach involves altering a symmetric ringcoupled to a disk clamp. Cutting, drilling, or punching are used toalter the ring.

A second approach involves drilling one or more holes in either the diskclamp or the spindle motor hub. The spindle motor hub is a spindle motorregion containing the screw holes used to couple with the disk clampwhen making the disk pack. Machining holes in the disk clamp or thespindle motor hub may introduce contaminants such as machine tailingsand machine oils. Furthermore, the machining required is specific to theparticular disk pack and must meet narrow tolerances, making thisapproach expensive.

A third approach involves injecting glue and/or heat sealing plastic atselected spots, and in selected amounts, near the disk clamp tocounterbalance the disk pack. This injection releases contaminants,which require cleaning procedures to restore the cleanliness of the disksystem when assembled. The injected compounds also require a specificenvironment in order to harden correctly, further adding cost, and oftendelays, until the hardening process is completed.

Accordingly, what is needed are counterbalances, and methods ofbalancing disk packs using such counter balances, which do not requireunit specific machining and which do not create contamination problems.

BRIEF SUMMARY OF THE INVENTION

The present invention includes methods of making a balanced disk packfrom a disk pack that may have previously been unbalanced. The inventionalso includes the balanced disk packs resulting from balancing the diskpacks, as well as the hard disk drives built with such balanced diskpacks. The invention further includes the apparatus making a balanceddisk pack from a disk pack.

The disk pack typically includes a spindle motor rigidly coupled with adisk clamp, and aligned by at least two open screw holes. The disk packbalancing methods use no unit-specific machining operations. Usingcleaned counterbalances minimizes contamination, which may eliminate thecost and production delays of glues and injected plastics.

The invention includes at least one mechanical counterbalance forbalancing a disk pack. The mechanical counterbalance fits into an openscrew hole, and locks against a locking plate collection member. Thelocking plate collection typically includes the disk clamp and thespindle motor.

The disk clamp may be the preferred locking plate collection member,because if the disk pack with locked mechanical counterbalances fails tobalance, disassembling can salvage at least the spindle motor and disks.

Preferred mechanical counterbalances include a cylindrical shaft rigidlycoupled to a latching assembly and a balance weight. The cylindricalshaft centers around a primary axis. The latching assembly includes acompressible latch rigidly coupled to a latch gap zone. The balance headrigidly couples to the latch gap zone. The latching assembly, includingthe compressible latch, and the latch gap zone, center around theprimary axis.

The invention includes selecting a counterbalance from a counterbalancetype collection of at least two counterbalances with total masses, whichare different or distinct. Such counterbalances will be referred to asdistinct total masses.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention, which are believed tobe novel, are set forth with particularity in the appended claims. Thepresent invention, both as to its organization and manner of operation,together with further objects and advantages, may best be understood byreference to the following description, taken in connection with theaccompanying drawings, in which:

FIG. 1 shows an exploded schematic view of a balanced disk pack in ahard disk drive;

FIG. 2 shows a side cross-sectional view of the disk pack in the harddisk drive of FIG. 1;

FIG. 3 shows a perspective view of the disk pack of FIGS. 1 and 2;

FIG. 4 shows a more detailed view of the cross-section of FIG. 2;

FIG. 5A shows a top cross-sectional view of a mechanical counterbalanceof FIGS. 1 to 4;

FIG. 5B shows a perspective view of the mechanical counterbalance ofFIGS. 1 to 5A;

FIG. 5C shows a side view of the mechanical counterbalance of FIGS. 1 to5B;

FIG. 5D shows the view along a cut line of the fins of FIG. 5C;

FIG. 6A shows a top cross-sectional view of a second preferredmechanical counterbalance which could be used in FIGS. 1-4;

FIG. 6B shows a side view of the second mechanical counterbalance ofFIG. 6A;

FIG. 6C shows a side cross-sectional view of the second mechanicalcounterbalance of FIGS. 6A-6B;

FIG. 7 shows an apparatus for making a balanced disk pack from a diskpack;

FIG. 8 shows a preferred apparatus for making the balanced disk pack asin FIG. 7;

FIG. 9A shows a detail of the program system of FIG. 8;

FIG. 9B shows a detail performing the balance operation for the openscrew hole of FIG. 9A;

FIG. 10A shows a detail selecting a mechanical counterbalance for theopen screw hole of FIG. 9B;

FIG. 10B shows a detail of inserting the selected counterbalance intothe open screw hole until the mechanical counterbalance locks into theopen screw hole of FIG. 9B;

FIG. 11A shows a detail of selecting the mechanical counterbalance forthe open screw hole of FIG. 9B;

FIG. 11B shows a detail of inserting the selected counterbalance intothe open screw hole of FIG. 9B;

FIG. 12A shows of locking the selected counterbalance into the openscrew hole of FIG. 11B;

FIG. 12B shows further making the balanced disk pack of FIGS. 8 and 9A;

FIG. 13A shows further locking the mechanical counterbalance into theopen screw hole of FIG. 11B;

FIG. 13B shows further analyzing the disk pack for the balancingoperation for the open screw hole of FIG. 9B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is provided to enable any person skilled inthe art to make and use the invention and sets forth the best modespresently contemplated by the inventors for carrying out the invention.Various modifications, however, will remain readily apparent to thoseskilled in the art, since the generic principles of the presentinvention have been defined herein.

The invention includes using at least one mechanical counterbalance 100for balancing a disk pack of a hard disk drive as shown in FIGS. 1 to 4.FIGS. 1 to 4 show a disk pack. A disk pack includes a spindle motor 80and at least one disk 12 rigidly coupled with the disk clamp 82. Thedisk pack is aligned by at least two open screw holes 85-A and 85-B.Disk packs may further include disk spacers 84. Open screw holes 85-Aand 85-B are shown only in FIG. 4.

FIG. 1 shows an exploded schematic view of a hard disk drive 10,including a balanced disk pack employing a preferred mechanicalcounterbalance 100. The hard disk drive 10 also includes the following.A hard disk drive base plate 90, a hard disk drive base 92, a seconddisk 14, separated by a disk spacer 84, a voice coil actuator 30, andthe hard disk drive cover 94.

FIG. 2 shows a side cross-sectional view of hard disk drive 10 with themechanical counterbalance 100 of FIG. 1 inserted into open screw hole85-C of the disk pack, at least partially creating the balanced diskpack.

FIG. 3 shows a perspective view of the balanced disk pack of FIGS. 1 and2. Two mechanical counterbalances 100-A and 100-B are inserted into twoopen screw holes in disk clamp 82. The Figure also includes a disk ring86, disk spacer 84, and disk 12.

FIG. 4 shows a magnified view of a portion of the cross-section of FIG.2. The mechanical counterbalance 100 is shown locking against the diskclamp 82. When fitted into the open screw hole 85-C, the mechanicalcounterbalance 100 aligns with both the disk clamp 82 and the spindlemotor 80.

The mechanical counterbalance 100, in FIGS. 2 and 4, includes means forfitting into the open screw hole, and locking against a locking platecollection member.

The locking plate collection of FIGS. 1 to 4 includes the disk clamp 82and the spindle motor 84. The locking plate collection may also includethe disk spacer 84 coupled between the disk clamp 82 and the spindlemotor 80.

Typically, disk spacers do not include screw holes, thus the diskspacers 84, of FIGS. 1 to 4, may or may not include screw holes. In harddisk drives possessing more than one disk, the disk pack furtherincludes one or more additional disk spacers 84, as seen in FIG. 1. Adisk pack may also include disk spacer 84 in hard disk drives using justone disk 12, as in FIGS. 2, 3 and 4.

FIGS. 5A to 6C show various embodiments of the mechanicalcounterbalances 100 of FIGS. 1 to 4.

The mechanical counterbalance 100 in FIGS. 5A to 5C includes acompressible latch 130 as a compressible ridge ring. FIGS. 5A, 5B and 5Cshow a top cross-sectional view, a perspective view, and a side view ofthe mechanical counterbalance 100 of FIGS. 1 to 4.

The mechanical counterbalances 100 of FIGS. 5A to 6C include acylindrical shaft 120 rigidly coupled to a latching assembly 130 to 140and a balance weight 110. The cylindrical shaft 120 is centered around aprimary axis 122. The latching assembly 130 to 140 is also centeredaround primary axis 122. The latching assembly 130 to 140 includes acompressible latch 130 rigidly coupled to latch gap zone 140. Thebalance head 110 rigidly couples to the latch gap zone 140.

The compressible latch 130 in FIGS. 5D to 6C is a ring of threecompressible fins. FIG. 5D shows the view along cut line 102, of FIG.5C, for the fins 132, 134, and 136. FIG. 6A, 6B and 6C show topcross-sectional, side, and side cross-sectional views of a preferredmechanical counterbalance 100. The compressible latch 130 may includetwo or more fins.

The mechanical counterbalance 100 of FIGS. 5A to 6C may be primarilycomposed of one material formed into the cylindrical shaft 120, thelatching assembly 130 to 140 and the balance weight 110. The materialmay essentially be a castable material, such as plastic. The plastic maypreferably be a version of nylon. In alternate embodiments, thecounterbalance 100 maybe formed of several different materials.

The mechanical counterbalance 100 may preferably be free ofcontaminants. Example contaminants include a particle larger than afirst specification, a hanging burr larger than a second specification,and a contaminant determined by a third specification. Each of thesespecifications is derived from a reliability specification used in themanufacturing of the hard disk drive.

The balance weight 110 of FIGS. 5A to 6C includes an interior face 112,exterior face 114, and side faces 116 and 118.

Mechanical counterbalance 100 has a total mass at essentially theprimary axis 122 (FIGS. 5A, 5B, 6A, and 6B) when balancing the diskpack. Mechanical counterbalance 100 preferably balances the disk pack byfitting the primary axis 122 through the center of the open screw hole85-C.

As in FIGS. 2 and 3, the following occurs when inserting the mechanicalcounterbalance 100 of FIGS. 5A to 6C into an open screw hole of the diskpack. The cylindrical shaft 120 fits into the open screw hole. Thecompressible latch compresses while passing through the screw hole, andexpands after passing through the screw hole to lock the mechanicalcounterbalance 100 against a locking plate collection member.

FIGS. 5A-6C also show the following. The means 120 for fittingmechanical counterbalance 100 into at least one open screw hole 85. Themeans for locking mechanical counterbalance 100 into the open screw holeagainst a locking plate collection member, after fitting mechanicalcounterbalance 100 into the open screw hole 85. The means for lockingincludes the compressible latch 130, the latch gap zone 140, and thebalance head 110.

FIGS. 7 and 8 show two embodiments supporting the invention's balancingmethod for disk packs.

The invention includes a method of balancing a disk pack involvingselecting a mechanical counterbalance from a counterbalance typecollection. The counterbalance type collection comprises at least twocounterbalances, each with a distinct total mass. In experiments by theinventors, two counterbalances had total, preferred masses of about 24mg and 54 mg.

FIG. 7 shows an apparatus for making a balanced disk pack 420 from adisk pack 410. The disk pack 410 includes a spindle motor 80 rigidlycoupled with a disk clamp 82. The spindle motor 80 aligns with the diskclamp 82 by at least two, and preferably four, open screw holes 85-A to85-D.

FIG. 8 shows a preferred apparatus for making a balanced disk pack 420from a disk pack 410 as in FIG. 7. The method uses an assemblyworkstation 400 controlled by a computer executing a program system 530of program steps residing in memory 520.

The mechanical counterbalance mass collection 450 includes at least twomembers 460 and 462. The mechanical counterbalance mass collectionmembers are the distinct total masses of the types 480 and 482 of themechanical counterbalance type collection, as in FIGS. 7 and 8.

As shown in FIG. 7, arrows 324 and 422 preferably represent means forinserting the selected counterbalance 102 into the screw hole.

Discussion of making balanced disk packs hereafter will be in terms ofthe flowcharts of program system 530 of FIG. 8. This simplifies thediscussion, and is not meant to limit the scope of the claims. FIGS. 9Ato 13B show the method of balancing a disk pack, using the invention'smechanical counterbalance.

The following flowcharts of the methods of the invention possess arrowswith reference numbers. These arrows signify flow of control, andsometimes data. The arrows support implementations including at leastone program step, or program thread, executing upon a computer,inferential links in an inferential engine, state transitions in afinite state machine, or learned responses within a neural network.

The operation of starting a flowchart refers to at least one of thefollowing. Starting may refer to entering a subroutine in a macroinstruction sequence in a computer. Starting may refer to entering intoa deeper node of an inferential graph. Starting may refer to directing astate transition in a finite state machine, possibly while pushing areturn state. Starting may refer to triggering a collection of neuronsin a neural network.

The operation of termination in a flowchart refers to the completion ofoperations. It may result in a subroutine return, traversal to a highernode in an inferential graph, popping of a previously stored state in afinite state machine, and/or return to dormancy of firing neurons in aneural network.

A computer as used herein will include, but is not limited to, aninstruction processor. The instruction processor includes at least oneinstruction processing element and at least one data processing element,each data processing element controlled by at least one of theinstruction processing elements.

FIG. 9A shows a program system 530 of FIG. 8 for making the balanceddisk pack 420 from the disk pack 410, for each of the open screw holes85. Operation 1002 analyzes the disk pack 410 for a balancing operationfor the open screw hole. Operation 1012 performs the balance operationfor the open screw hole.

FIG. 9B shows a detail of operation 1012 of FIG. 9A, if a balance actionis determined for the open screw hole. Operation 1032 selects amechanical counterbalance for the open screw hole to create a selectedcounterbalance 102 of a total mass. Operation 1042 inserts the selectedcounterbalance 102 into the open screw hole, until the selectedcounterbalance locks into the open screw hole, at least partiallycreating the balanced disk pack.

FIGS. 10A and 10B show one of several possible, equivalentimplementations of the operations of FIG. 9B, including implementationswith a shared test.

FIG. 10A shows a detail of operation 1032 of FIG. 9B. Operation 1132determines if a balance action is needed for the open screw hole. Whenthe determination 1134 is Yes, operation 1136 selects a mechanicalcounterbalance for the open screw hole to create a selectedcounterbalance 102 of a total mass.

FIG. 10B shows a detail of operation 1042 of FIG. 9B. Operation 1152determines whether the open screw hole needs a balance action. When thedetermination 1154 is Yes, operation 1156 inserts the selectedcounterbalance 102 into the open screw hole until the selectedcounterbalance 102 locks into the open screw hole at least partiallycreating the balanced disk pack.

FIG. 11A shows a detail of operation 1032 of FIG. 9B. Operation 1172selects the mechanical counterbalance for the open screw hole from thecounterbalance collection 470 and from the counterbalance masscollection 450, creating the selected counterbalance 102 with the totalmass, as shown in FIGS. 8 and 9.

In FIGS. 7 to 11A, the selected counterbalance 102 is an instance of amember of the mechanical counterbalance collection 470.

The arrows in FIGS. 7 and 8 pointing to and pointing from the selectedcounterbalance 102 preferably represent assembly feed mechanisms.

FIG. 11B shows a detail of operation 1042 of FIG. 9B. Operation 1192fits the selected counterbalance 102 into the open screw hole. Operation1202 locks the selected counterbalance 102 into the open screw holeagainst a locking plate collection member, after fitting the selectedcounterbalance into the open screw hole.

FIG. 12A shows a detail of operation 1202 of FIG. 11B. Operation 1202locks the selected counterbalance 102 into the open screw hole againstthe disk clamp after fitting the selected counterbalance into the openscrew hole.

FIG. 12B shows a detail of program system 530 of FIGS. 8 and 9Aproviding, if the disk pack fails to balance, disassembly of the diskpack with fitted counterbalances to salvage at least the spindle motorand the disks. This is performed as follows. Operation 1242 confirms abalance failure for the disk pack. Operation 1252 removes the diskclamp, and all of the mechanical counterbalances locked to the diskclamp, from the disk pack to create a partial disk pack. Operation 1262then rigidly couples a second disk clamp to the spindle motor of thepartial disk pack, and aligns it by open screw holes, to recreate thedisk pack.

FIG. 13A shows a detail of operation 1202 of FIG. 11B. Operation 1302compresses a compressible latch into the open screw hole. Operation 1312expands this latch after compressing it into the open screw hole to lockthe mechanical counterbalance against the locking plate collectionmember.

FIG. 13B shows a detail of operation 1002 of FIG. 9B. Operation 1352uses a disk pack balance instrument 304 of FIG. 8 to analyze the diskpack 410 for the balancing operation. Hoffman manufactures the preferreddisk pack balance instruments.

Those skilled in the art will appreciate that various adaptations andmodifications of the just-described preferred embodiments can beconfigured without departing from the scope and spirit of the invention.Therefore, it is to be understood that, within the scope of the appendedclaims, the invention may be practiced other than as specificallydescribed herein.

1. A method of making a balanced disk pack, for a hard disk drive, froma disk pack including a spindle motor rigidly coupled, and aligned by atleast two open screw holes, with a disk clamp, wherein said methodcomprises, for each of said open screw holes, of the steps of: analyzingsaid disk pack for a balancing operation for said open screw hole;performing said balance operation for said open screw hole, furthercomprising said steps of: selecting a mechanical counterbalance,comprising a cylindrical shaft centered around a principal axis and abalance head asymmetric about said principal axis including a concaveinterior face and a convex exterior face, for said open screw hole tocreate a selected counterbalance of a total mass, if a balance action isdetermined for said open screw hole; and inserting said selectedcounterbalance into said open screw hole until said mechanicalcounterbalance locks into said open screw hole with said concaveinterior face locked toward said spindle motor and with said convexexterior face locked away from said spindle motor to at least partiallycreate said balanced disk pack, if said balance action is determined forsaid open screw hole.
 2. The method of claim 1, wherein the stepselecting said mechanical counterbalance for said open screw holefurther comprising the step of: selecting said mechanical counterbalancefor said open screw hole from a counterbalance collection and from acounterbalance mass collection to create said selected counterbalancewith said total mass; wherein said mechanical counterbalance masscollection comprising at least two members; wherein said total mass is amember of said mechanical counterbalance mass collection; wherein eachof said members of said mechanical counterbalance mass collectionapproximates the total mass of at least one member of said mechanicalcounterbalance collection; and said selected counterbalance is aninstance of a member of said mechanical counterbalance collection. 3.The method of claim 1, wherein the step inserting said selectedcounterbalance into said open screw hole further comprising the stepsof: fitting said selected counterbalance into said open screw hole withsaid concave interior face locked toward said spindle motor and withsaid convex exterior face locked away from said spindle motor; andlocking said selected counterbalance into said open screw hole against amember of a locking plate collection after fitting said selectedcounterbalance into said open screw hole; wherein said locking platecollection comprising said disk clamp and said spindle motor.
 4. Themethod of claim 3, wherein the step locking said mechanicalcounterbalance into said open screw hole further comprising the stepsof: compressing a compressible latch in said open screw hole; andexpanding said compressible latch after compressing said compressiblelatch in said open screw hole to lock said mechanical counterbalanceagainst said locking plate collection member.
 5. The method of claim 4,wherein said compressible latch includes at least one member of a latchcollection comprising a compressible ridge ring, and an M compressiblefin ring; wherein M is at least two.
 6. The method of claim 5, whereinsaid locking plate collection further comprising at least one diskspacer.
 7. The method of claim 5, wherein the step locking said selectedcounterbalance into said open screw hole further comprising the step of:locking said selected counterbalance into said open screw hole againstsaid disk clamp after fitting said mechanical counterbalance into saidopen screw hole; wherein said method further comprising the steps of:confirming a balance failure of said disk pack after locking saidmechanical counterbalance; removing said disk clamp and all of saidmechanical counterbalances locked to said disk clamp to create a partialdisk pack; and rigidly coupling a second disk clamp to said spindlemotor of said partial disk pack, and aligning by said open screw holes,to recreate said disk pack.
 8. The method of claim 1, wherein the stepanalyzing said disk pack for said balancing operation for said openscrew hole further comprising the step of: using a disk pack balanceinstrument to analyze said disk pack for said balancing operation.
 9. Amethod of making a hard disk drive, comprising the step of: using saidbalanced disk pack of claim 8 to create said hard disk drive.